It seems unlikely that there would be hoglets already. The gestation period is about 35 days which would mean that the female would have had to become pregnant before the beginning of April and many of the females (depending where you are in the country) weren’t back until much later in April. Also when they first return from hibernation they usually need to put on a bit of weight. If hoglets were not with their Mother they would probably be roughly 6 – 8 weeks old. Which would mean the gestation period beginning much earlier.
One possibility, is that female youngsters which have been overwintered in captivity may have been released earlier, but may not be old enough to breed yet. They become sexually mature approx. 7 – 9 months old.
There are a few hogs who choose not to hibernate. I had one here. But only one. I suppose it is possible that if there were two in the same area a female could have become pregnant really early. But finding food at that time of year is more difficult so would they have had time to go through the courtship procedure?
I wonder if there is some other explanation. Is there any chance you could be mistaken. Pictures on film can often be quite deceiving. Alternatively, I have heard of people releasing pet African Pygmy Hedgehogs into the wild – they are a bit smaller. In that case they may have different colouring from our European Hedgehogs.
Interesting – and hedgehogs do seem to like to keep us guessing!